Explosion proof plug and receptacle



March 17, 1964 I A. I. APPLETON 3,125,394

- EXPLOSION PROOF PLUG AND RECEPTACLE Filed Oct. 28, 1960 4 Sheets-Sheet 1 INVENT OR.

I Mai-ch 17, 1964 A. I. APPLETON EXPLOSION PROOF PLUG AND RECEPTACLEFiled Oct. 28, 1960 4 Sheets-Sheet 2 BY w mm; WQWM.

March 17, 1964 A. l. APPLETON EXPLOSION PROOF PLUG AND RECEPTACLE 4Sheets-Sheet 3 Filed Oct. 28, 1960 March 17, 1964 A. 1. APPLETONEXPLOSION PROOF PLUG AND RECEPTACLE 4 Sheets-Sheet 4 Filed Oct. 28, 1960United States Patent 3,125,394 EXPLOSION PROOF PLUG AND RECEPTACLEArthur I. Appleton, Northbrook, Ill. (1713 Wellington Ave., Chicago 13,Ill.) Filed Oct. 28, 1960, Ser. No. 65,642 13 Claims. (Cl. 339-111) Thepresent invention relates to electrical plugs and receptacles. Moreparticularly the invention relates to explosion proof electricalfittings of the type comprising a telescopically operative plug andreceptacle having cooperating terminals and incorporating a delayedaction construction so that a momentary time delay occurs duringinsertion or withdrawal of the plug from the receptacle, in order toinsure that any are formed between the respective terminals isextinguished before the plug and receptacle are completely separated.

The invention has, as its principal object, a simple and improved plugand receptacle structure affording positive, safe, and foolproofprotection in explosive atmospheres.

More specifically, it is an object of this invention to incorporate intosuch a plug and receptacle an improved delayed withdrawal action betweenthe plug and the receptacle in which it is telescopically received sothat a delay is imparted as the plug terminals are separated from thereceptacle terminals whereby any arc which is formed is extinguishedbefore the plug is completely withdrawn from the receptacle.

Another object of the invention is to provide an improved plug andreceptacle of the foregoing character in which a two step delayedwithdrawal is provided in a simple and reliable manner and which devicecan be manually operated by even the most inexperienced user.

A more detailed object of the present invention is to provide areceptacle of the foregoing character which is foolproof in itsoperation and which cannot be tampered with to avoid a two stepwithdrawal of a plug without destroying the operation of the receptacle.

It is a further object of the invention to provide an improved two steptype receptacle which can receive conventional type plugs and yetinsures a two step withdrawal action. It is a related object to providean improved plug which, While incorporating the objects of thisinvention, is interchangeable with conventional commercial receptacles.

Still another object of the invention is to mount a hinged cover on areceptacle of the foregoing character in such a manner that thereceptacle can be easily and readily operated to receive or release aplug with a two step delayed action and yet can be completely closedwhen the plug is removed.

Still a further object of the invention is to provide an improved pluglocking safety mechanism which prevents accidental disconnection of theplug and receptacle.

Other objects and advantages of the present invention will becomeapparent as the following description proceeds taken in connection withthe accompanying drawings wherein:

FIGURE 1 is an elevation view of a plug and receptacle embodying thepresent invention.

FIG. 2 is a view taken substantially in the plane of line 2-2 of FIG. 1and illustrating a plug mounted in the receptacle with the receptaclecover held open.

3,125,394 Patented Mar. 17, 1964 ice FIG. 3 is a view takensubstantially in the plane of line 3-3 of FIG. 1 and illustrating thecover slide and lock arrangement.

FIG. 4 is a fragmentary section view of a plug and receptacle embodyingthe present invention with the plug in its initial stages of insertionor final stage of withdrawal from the receptacle.

FIG. 5 is a section View taken substantially in the plane of line 5-5 ofFIG. 4.

FIG. 6 is a fragmentary section view of the plug and receptacle shown inFIG. 4 but with the plug in an intermediate position of engagement orwithdrawal.

FIG. 7 is a section view taken substantially in the plane of line 7-7 ofFIG. 6.

FIG. 8 is a fragmentary section view of the plug and receptacle shown inFIG. 4 and with the plug and receptacle in complete engagement.

FIG. 9 is a perspective view of a cover hinge and slide block used inthe receptacle embodying the present invention.

FIG. 10 is an elevation view of a modified form of receptacle embodyingthe present invention.

FIG. 11 is a vertical section View through a plug and receptacle of thecharacter shown in FIG. 10.

FIG. 12 is a section view taken substantially in the plane of line 12-12on FIG. 11 and illustrating an improved cable clamping device.

FIG. 13 is a perspective view of a slide block used in the receptacle ofthe type shown in FIGS. 10 and 11.

FIG. 14 is a section view taken substantially in the plane of line 14-14on FIG. 11 and illustrating a receptacle with the slide in position forinitially receiving a plug.

FIG. 15 is a View similar to FIG. 14 but with the plug inserted and theslide in a position wherein the plug can be completely inserted withinthe receptacle.

FIG. 16 is a view similar to FIG. 14 but showing the plug completelyinserted and the slide in a locking position.

FIG. 17 is a view taken substantially in the plane of line 17-17 of FIG.11 and showing the terminals on the receptacle.

FIG. 18 is a fragmentary section view taken substantially in the planeof line 18-18 on FIG. 17 and illustrating a locking construction for thereceptacle contacts.

While certain illustrative embodiments of the present invention havebeen shown in the drawings and will be described below in considerabledetail, it should be understood that there is no intention to limit theinvention to the specific forms disclosed. On the contrary, theintention is to cover all modifications, alternative constructions,equivalents and uses falling within the spirit and scope of theinvention as expressed in the appended claims.

In general, my invention relates to an explosion proof plug andreceptacle each having cooperating terminals therein. The plug is of aconventional type and has one or more radially extending arcuateshoulders thereon. In accordance with my invention, means are providedfor applying a two step withdrawal for engagement between the plug andreceptacle. To impart such a time delay, there is provided on thereceptacle a hinged cover and slide, the slide providing a pair ofopposed stops which engage with the shoulder on the plug as the plug isrespectively inserted or withdrawn. In this manner, any are which mightbe formed between the corresponding terminals as they are separated isextinguished before the plug is completely withdrawn from thereceptacle.

The socket member FIGS. 1-9 comprises a suitable tubular casing havingmounted therein an internal insulating block 11 formed with axiallyextending chambers 12 in which are mounted terminals 13. These chambersare generally arc-tight passages which completely surround theterminals. The casing or housing is mounted on a siutable support bymeans of a mounting flange 14 through which electrical wires enter.These wires are secured to the terminals 13 on the terminal mountingblock 11 which is mounted in the casing in an improved manner, shown inFIGS. 17 and 18, which will be described in detail.

The plug member likewise comprises a tubular casing 16 which isdimensioned to fit within the receptacle housing 10. For coaction withthe receptacle terminals 13 there is mounted within the plugcorresponding plug terminals 18. The latter are generally sleeve shapedmembers adapted to slide within the arc-tight chambers 12 and engagearound the receptacle terminals 13. If desired, the various terminalsmay be of different sizes or cross sectional shapes so that the plug canbe inserted in only one orientation.

The plug 16 is provided, at the end opposite from the terminals, with asuitable clamping device 19 for receiving and holding a cable 20containing electrical wires, an improved form of which is shown in FIGS.11 and 12 and will be described in detail. These wires are connected tothe plug terminals by solder type connections in which the ends of thewires are permanently attached to the internal ends of the plugterminals 18.

The plug and receptacle construction thus far described, with theexception of the noted improvements, is generally conventional in theart. Many such plugs also include a pair of diametrically oppositeradially extending projections 21, 22 which are are shaped and extendoutwardly from the plug intermediate its ends. These shouldersconventionally serve as stops for use in delayed action devices nowknown in the art such as the device described in US. Patent 2,002,177.In order to orient the plug within the receptacle, these shoulders arealso each a different slze.

In accordance with one aspect of the present invention, novel means areprovided for obtaining a two step withdrawal of a plug from a receptaclewhich means makes use of a radially extending arcuate projection 22 onthe plug. One illustrative means embodying the invention comprises aslide 25 shown in perspective in FIG. 9. Referring to FIGS. 1-9, theslide 25 is mounted in a sleevelike extension 26 of the receptaclehousing 10 for transverse sliding movement with respect to thelongitudinal axis of the receptacle and in position for selectiveengagement with one arcuate projection 22 on the plug 16. For providingthe necessary stops to effect a delayed withdrawal, the upper surface ofthe slide 25 is formed with a pair of spaced parallel relieved ordepressed arcuate areas 28, 29. These areas are connected by a channel30 which defines, with the relieved areas, a pair of opposed spaced stopsurfaces or shoulders 31, 32. These shoulders 31, 32 face each other butare spaced apart transversely along the slide 25.

The slide is mounted in the receptacle housing extension 26 fortransverse sliding movement and the relieved areas are cut to asutficient depth to receive and pass the plug shoulder 22. Referringmore specifically to FIG. 9, as the plug 16 is inserted into thereceptacle, the plug shoulder 22 passes through the first relieved area23, in the direction of the dotted arrow a and engages against the stopshoulder 31. The slide is then pushed transversely, in the direction ofthe solid arrow A, so that the plug shoulder 22 is positioned in thechannel 30 and in front of the second relieved area 29. The plug canthen be inserted further into the receptacle, in the direction of thedotted arrow [7, so that the respective terminals are engaged. It willalso be appreciated that when the terminals are engaged the slide cannotbe returned inasmuch as the relieved area 29 will not slide past theplug shoulder 22. This sequence of steps is shown in FIGS. 4-8,inclusive.

In order to produce an improved and simplified plug delay action, theoperation of the slide and cover are correlated. To this end, the slidesupports a hinged cover for closing the open plug receiving end of thereceptacle. For this purpose, the slide 25 includes a pair of spaceddepending ears 34 provided at their lower ends with an aperture 35 inwhich a pivot pin 36 is received. This pin hingeably supports a cover38, the cover having a hinge mounting portion 39 extending substantiallyat right angles to the main cover portion and provided with an aperturethrough which the pin 36 passes.

For holding the cover in an open position when a plug 16 is insertedinto the receptacle 10, a suitable key and slot arrangement is providedbetween the cover 38 and a plate 4% which serves to hold the slide 25 inposition on the receptacle. To this end, the plate 40 is generallyT-shaped and extends between the ears of the slide and is secured ateach of its extremities to the receptacle housing portion 26, as shownin FIG. 3. Depending from the plate at an intermediate point and betweenthe ears of the slide is a key 41 adapted to engage in a slot 42 definedin the projecting hinge portion 39 of the cover 38. So that the covermay close when the plug is withdrawn, the projecting portion 39 includesa cut out or relieved area 43 (FIG. 5 which is wide enough to receivethe key and allow the cover to swing upwardly under the force of aspring mounted between the cover and the receptacle. When the cover isswung downwardly to expose the receptacle, and a plug is inserted, thekey 41 is initially positioned in front of the slot 42. After the plugis inserted so that the plug shoulder 22 engages the first stop shoulder31, the slide and cover is then moved laterally relative to thereceptacle. This positions the plug shoulder 22 in front of the relievedarea 29 and at the same time engages the key 41 in the slot 42 on thecover 39. The cover is thus held open when the slide is moved so that itis not urged closed and does not ride up against the plug.

A modified form of plug and receptacle embodying the present inventionis shown in FIGS. 10-18, inclusive. In this modification, the operationof the time delay slide and the cover is similarly correlated; howeverthe slide is mounted for movement independent of the cover and the coveris mounted directly on the receptacle so that only the slide is movedback and forth. In describing this form of the invention, referencecharacters similar to those used above will be employed with thedistinguishing addition of a prime mark. Thus, in describing thismodification, the slide will be identified as element 25'.

In the modification shown in FIGS. 1018, as in the modification shown inFIGS. 19, there is provided a receptacle comprising a tubular casing 10,in which is mounted a terminal block 11, the casing having a mountingflange 14 by which the receptacle can be mounted on a junction box orthe like. The receptacle is adapted to receive a plug comprising atubular casing 16' dimensioned to fit within the receptacle casing 10and carrying terminals 13' engageable with corresponding terminals 13'in the receptacle terminal block 11' (FIGS. 1416).

For receiving the plug with a time delay action, the receptacle isprovided with a sleeve-like extension 26 as described above in which ismounted a transversely shiftable time delay slide 25' engageable with anextending arcuate projection 22' on the plug. As in the slideconstruction described above, the upper surface of the slide 25 isformed with a pair of spaced parallel relieved or depressed arcuateareas 28, 29. These areas are connected by a channel 30' which defineswith the relieved areas 23', 2%, a pair of opposed spaced stop surfacesor shoulders 31, 32. As described above, these shoulders 31, 32 faceeach other but are spaced apart transversely along the slide 25. Theoperation of the slide is the same as described above in connection withthe slide 25 shown in FIG. 9.

Referring more specifically to FIG. 13, as the plug is inserted into thereceptacle, the plug shoulder 22 passes through the first relieved area28, in the direction of the dotted arrow a and engages against the stopshoulder 31'. The slide is then pushed transversely, in the direction ofthe solid arrow A, so that the plug shoulder 22' is positioned in thechannel 30 and in front of the second relieved area 29". The plug canthen be inserted further into the receptacle, in the direction of thedotted arrow 17', so that the respective terminals are engaged. It willalso be appreciated that when the terminals are engaged the slide cannotbe returned inasmuch as the relieved area 29' will not slide past theplug shoulder 22'. This sequence of steps is shown in FIGS. 14-16inclusive.

Provision is made in this modification for locking the plug againstWithdrawal from the receptacle. To this end, a third relieved area 33 isprovided along the edge of the slide opposite from the first relievedarea 23' and opening into relieved area 29'. This relieved area definesa shoulder 37 opposite from shoulder 31. When the plug is completelyinserted into the receptacle as shown in F168. 16 and 17, the slide 25can 'be pushed partially back, in the direction of solid arrow B' toposition the shoulder 37 behind the plug shoulder or projection 22',thereby locking the plug against withdrawal.

For enclosing the plug receiving opening of the receptacle, theconstruction of which is essentially the same as described above withreference to FIGS. 1-9, a cover 38 is hingeably supported between a pairof spaced depending ears 34 secured to a plate 45 fastened across a pairof lugs or ridges 46 depending from the receptacle housing 26'. Theplate 45 together with the depending lugs 46 defines a slot 47 whichopens into the interior of the receptacle housing 26. As describedabove, the hinge connection is formed by a pivot pin 36' mounted inapertures 35' in the depending cars 34 and a spring 48 mounted in anaperture 49 in the cover and engaged between the cover and the pin 36',serves to bias the cover to a closed position.

The slide 25 is positioned in the slot 47 defined in the portion 26' ofthe receptacle and enclosed by the plate 45 on which the cover ismounted. In this modification, the lower surface of the slide 25' isformed with an extending key 51) which projects through a slot 51 in theplate and is positioned for engagement with a slot and shoulderarrangement 42' (FIG. 16) defined in the projecting hinge portion 39 ofthe cover 38'. The slot portion 42 is constructed in a manner such thatthe cover may close when the plug is withdrawn and the slide 25 ispositioned in the location shown in FIG. 14, that is with the slideextending outwardly of the slot towards the left. This is the positionthe slide assumes when moved in a direction opposite to the directionindicated by the solid arrow A shown in FIG. 13.

For engaging the slide and slide projection or key 5%), the projectingportion 39 of the hinge includes a cut out or relieved area 43' (FIG.15) which is wide enough to pass the key 5t and allow the cover to swingupwardly under the force of the spring 48. When the cover 38 is swungdownwardly to expose the receptacle and a plug is inserted thereinto,the key 5% being initially positioned in front of the slot 42 much inthe manner described above, the plug shoulder 22 engages the first stopshoulder 31 of the slide 25. The slide is then moved laterally relativeto the receptacle (in the direction of solid arrow A in FIG. 13). Thispositions the relieved area 29 of the slide in front of the plugshoulder 22' as described above, and at the same time engages the key5th in the slot 42' on the cover portion 39' as shown in FIG. 15. Thecover is thus held open and locked against the force of the spring. Theplug is then pushed all the way into the receptacle effecting engagementof the respective contacts.

The locking means, including the relieved area 33 and shoulder 37 on theslide 25 serve to prevent any slight withdrawal of the plug which mightdisengage the contacts. As can be seen in FIGS. 13 and 16, the slide canbe moved slightly back to lock the plug in position by engaging the plugshoulder 22' in the relieved area 33. When the slide is so moved (in thedirection of solid arrow B in FIG. 13), one portion of the key 5t]remains engaged in the hinge slot 42 so that the cover is held open asshown in FIG. 16.

Successive steps in the insertion or withdrawal of a plug from areceptacle embodying the present invention are shown in detail in FIGS.4-8, inclusive for the first modification, and in FIGS. 14- 16 for thesecond modification. Assuming that a plug has been completely inserted,as shown in FIG. 8, the plug terminals 1 8 are positioned within thechambers 12 and the respective plug and receptacle terminals 18 and 13are engaged. The plug shoulders 211, 22 are positioned against the endof the receptacle housing 10 and within the auxiliary housing 26. Theslide 25 is in its far right position as shown in FIG. 7 with the key 41engaged in the slot 42 holding the cover 38 open. The first step in thewithdrawal of the plug is to pull it outwardly as far as it will go sothat the plug shoulder 22 engages the stop shoulder 32 on the slide asshown in FIG. 6. In this position the plug terminals -18 are disengagedfrom the receptacle tenminals 16 but have not been removed from the aretight chambers 12 so that any arc occurring between the receptacle andthe plug terminals is extinguished. This position (FIG. 6) constitutesthe first withdrawal step or delay step.

To remove the plug from the receptacle, the slide 25 is pushed to itsfar left position as shown in FIG. 5. As this is done the plugshoulder-22 slides through the channel 3d and is positioned in front ofthe second slide relieved area 28 as shown in FIG. 5. This step alsoremoves the key 41 from the slot 42 and thereby releases the cover whichcan then swing upwardly. The plug is then removed, as shown in FIG. 4,with the plug shoulder 22 sliding out through the relieved area 28 inthe slide. When the plug is removed the cover swings upwardly to itsclosed position and the receptacle is completely enclosed.

The reverse procedure is followed to insert the plug and receptacle. Inthis procedure as the slide is moved to the right the cover is engagedwith the key depending from the slide plate so that the cover is held inan open position. As a safety feature, the cover must be held open whenthe plug is inserted. Otherwise, the slide cannot be moved to releasethe plug for insertion in the receptacle. Similarly, the slide cannot bemanipulated to permit the plug to be withdrawn in one continuous step.Starting with a closed receptacle, the operation of the unit is obviousand foolproof even when used by those inexperienced in handling heavyduty explosion proof connectors, and most important, the constructioninsures that a two step withdrawal of the plug from the receptacle mustbe followed so that any danger of an arc igniting an explosiveatmosphere surrounding the fitting is eliminated.

In addition to the above desirable features, the plug and receptacleconstruction embodying the invention has additional features which serveto enhance the ease of coupling the members together and improve thegripping of the cable attachment portion of the plug and therebyfacilitate handling of the plug. While the arcuate shoulders 21, 22afford an orienting action and also allow some play to facilitatealinement of the plug and receptacle contacts, means are provided toaccommodate the plug and receptacle contacts to slight misalinement ofthe contacts when the plug is force ably inserted into the receptacle.This is embodied in the receptacle and particularly in an improvedcontact block structure. AS shown in the drawings, the improvedreceptacle contact insulating block 11 is mounted within the receptaclehousing in a manner affording slight rotary movement. This has beenfound not only to facilitate insertion of the plug but also tosubstantially simplify the assembly of the receptacle contact and themounting of the contact block 11 in the receptacle housing 10. Thisstructure is shown in detail in FIGS. 11 and 17.

The terminal mounting or insulating block 11 is formed with means bywhich it may be removably mounted in the casing 10. One illustrativemeans, shown in FIGS. 11, 17 and 18, comprises a threaded portion on theblock 11 behind the contact carrying portion. The threaded portion 55terminates in an annular radially extending rear shoulder 56 defined bya rearrnost body member 53 which includes a plurality of apertures 59 inwhich are mounted terminal clips 61% which are electrically connectedwith the contact terminals 13 in the chambers 12 of the insulatingblock. The block 11 is threadably secured within the casing 16 and isheld in place by a screw 61 and washer 62 arranged on the casing. Thewasher extends over the shoulder 56, as shown in FIG. 18, to prevent thewithdrawal of the block 11. To accommodate the washer to engagement withthe shoulder 56, the latter includes a cutout portion 64, which isslightly larger than the washer, so that some play is permitted betweenthe washer 62 and the insulating block 11. This provision of playbetween the washer 62 and the block 11 enables the block 11 carrying thecontacts to rotate slightly when mounted in the casing and in thismanner accommodate the plug and receptacle contacts in cases of slightmisalignment.

As still another feature of the present invention, improved means areprovided for use in gripping the plug for withdrawing it from orinserting it into the receptacle, which gripping means contemplates theinclusion of means for securing the cable thereby to avoid loosening thecable connection. One such an illustrative means is shown in FIGS. 11and 12 of the drawings and comprises a cable gripping and sealingmember, indicated generally at 65, wluch can be mounted in sealingrelationship with the exposed end of the plug housing 16 and whichincludes a cable gripping means or clamp 66. More specifically, thecable gripping and sealing means comprises an outwardly flaredsleeve-shaped member 68 having a flange portion 69 at one end thereofdefining a bore 79 through which a cable 71 extends. The flange and boreterminate in a counterbore '72 defined by the sleeve-shaped member 68 inwhich the cable gripping clamp 66 is mounted. A second counterbore 74 isdefined by an extending sleeve portion 75 of the member 68 whichsurrounds the end of the plug casing 16. The counterbore sleeve portion75 defines with the intermediate bore 72 an internal shoulder 76 againstwhich is positioned an annular washer member 78 having an internalaperture '79, the diameter of which is approximately equal to that ofthe flange bore 70. This washer is supported within the member 68 bymeans of a pair of threaded screws 8t each having a reduced shank 81extending through the body portion defining the bore 72. The screws 89are formed with a head 82, and a fiber washer 84- on the shank 31 servesto hold the washer '78 in place. The threaded end of the screws areengaged with tapped holes in the end of the plug housing 16.

For purposes of gripping the cable within the housing 65 the cable clamp66 is formed with a pair of opposed clamp members 85 (FIG. 12) eachhaving a shallow arcuate center portion 86 engageable with opposite sideportions of a cable. For gripping the cable 71, the arcuate portion 66of the cable clamp members 35 has an outwardly punched portion 8%defining at the inner surface a recess 39 (FIG. 11) so that when theclamp is tightened against the cables the resilient cable sheath isdeformed into this recess. As a result the gripping action of the clampon the cable is substantially increased. The clamp members 85 aretightened together by a pair of opposed bolts 90 each of which isthreaded to receive a clamping nut 91. The clamp members are formed withsuitable apertures through which the bolts extend and the bolts areoriented in opposite directions with respect to each other so that whenthey are tightened the clamp members are squeezed together and grip thecable. In order to center the cable and hold it tightly within thehousing 65, one end of each clamp member 85 is engaged in a slot )2formed in the interior wall of the sleeve-shaped member 68 (FIG. 12).When the clamp bolts 86 are tightened, the ends of the clamping members85 are held within the slots 92 and each member 85 tends to swing aboutthat end as a pivot. The clamping bolts 96 extend through the wall ofthe member 68 and are provided with a suitable head 94 on their outerends for receiving a screwdriver or the like. In order to afford anouter surface on the sleeve 68 which is free of projections, eachclamping screw head Wt is recessed in a suitable aperture 95 in thesurface of the member 68.

For purposes of sealing the clamping member sleeve or body 68 onto theend of the plug casing "16, there is provided a sealing member 98. Thissealing member 98 is formed of a resilient, compressible material, forexample a suitable flexible compound such as neoprene rubber or thelike, which is compressed into sealing relation with the cable and theplug when positioned within the counterbore. In order to sealinglyengage the plug, the sealing member 98 is provided with a taperedexternal surface 87 which fits within a correspondingly tapered bore orsocket 99 in the end of the plug housing 16. To 'sealingly grip thecable, the internal surface of the resilient sealing member 98 ispreferably roughened such as by the provision of suitable corrugationsor threads 1%. To seal the cable 71 into the plug, the clamping member65 is tightened onto the end of the plug 16 so that resilient member 98is squeezed tightly into engagement with both the sealing washer 78 andthe tapered surface $9 of the plug casing 16. At the same time thiscompressing action will squeeze the corrugations 1% tightly intoengagement with the outer sheath of the cable thereby effecting anexplosion proof and a weather proof seal which is effective to preventthe access of moisture, gases, and the like to the interior of the plugwhere the terminal clips are located.

It will be appreciated that, in addition to the above features, manyothers are provided. The enlarged outwardly flaring outer surface of thebody portion or sleeve 68 will afford a grip on the end of the plug foreasing the insertion and withdrawal of the plug from the receptacle. Awaterproof seal is effected by the cooperation between the internalwasher 71 and the resilient sealing member 85. At the same time, thewasher 71 and sleeve 63 affords a suitable housing for the clampingmembers 76. Furthermore, the body portion 62 with the notches 92 afforda novel means for cooperating with the cable clamps to securely grip thecable and thereby relieve the plug terminal clips from any strain shouldthe plug be removed by pulling on the cable, while at the same time asmooth, projection free, yet substantial gripping surface is provided onthe cable end of the plug.

This application is a continuation-in-part of my copending application,Serial No. 852,082, filed November 10, 1959 and now abandoned.

I claim as my invention:

1. An explosion proof receptacle for use with a plug having a plug bodycarrying a plurality of plug terminals extending therefrom, an annularlyextending plug housing surrounding said plug terminals, and a radiallyextending arcuate shoulder on the outer surface of the plug housing,said receptacle comprising a receptacle body mounting a terminal blockhaving a plurality of receptacle terminals telescopically engageablewith the plug terminals, an

annular receptacle housing extending from said receptacle body in spacedsurrounding relation with said terminal block, said plug housing beingreceived within said receptacle housing and closely surrounding saidterminal block when the receptacle terminals are engaged with the plugterminals, a slide member mounted on said receptacle housing fortransverse sliding movement with respect thereto between oppositepositions, said slide member having means thereon defining opposedtransversely spaced stop shoulders for successively engaging the plugshoulder upon transverse movement of said slide member from one to theother of said opposite positions so as to afford a two step delayedwithdrawal and insertion of the plug respectively from and into thereceptacle, a cover hingedly mounted on said slide and biased forclosing the receptacle when the plug is removed therefrom and the slideis in one of said opposite positions, and means on said receptaclehousing engageable with said cover for holding the same open when theslide is in the other of said opposite positions wherein the plug isinserted in place within the receptacle.

2. An explosion proof receptacle for use with a plug having a plug bodycarrying a plurality of plug terminals extending therefrom, an annularlyextending plug housing surrounding said plug terminals, and a radiallyextending arcuate shoulder on the outer surface of the plug housing,said receptacle comprising a receptacle body mounting a terminal blockhaving a plurality of receptacle terminals telescopically engageablewith the plug terminals, an annular receptacle housing extending fromsaid receptacle body in spaced surrounding relation with said terminalblock, said plug housing being received Within said receptacle housingand closely surrounding said terminal block when the receptacleterminals are engaged with the plug terminals, a slide member mounted onsaid receptacle housing for transverse sliding movement with respectthereto between opposite positions, said slide member having meansthereon defining opposed transversely spaced stop shoulders forsuccessively engaging the plug shoulder upon transverse movement of saidslide member from one to the other of said opposite positions so as toafford a two step delayed withdrawal and insertion of the plugrespectively from and into the receptacle, a cover having an arm fixedthereto hingedly mounted on said slide, means engaged between said armand said slide for biasing said cover to close the receptacle when theplug is removed therefrom and the slide is in one of said extremepositions, a key member on said receptacle housing, and means defining aslot on said cover arm engageable with said key for holding the coveropen when the slide is in the other extreme position wherein the plug isinserted in place Within the receptacle.

3. An explosion proof receptacle for use with a plug having a plug bodycarrying a plurality of plug terminals extending therefrom, an annularlyextending plug housing surrounding said plug terminals, and a radiallyextending arcuate shoulder on the outer surface of the plug housing,said receptacle comprising a receptacle body mounting a terminal blockhaving a plurality of receptacle terminals telescopically engageablewith the plug terminals, an annular receptacle housing extending fromsaid receptacle body in spaced surrounding relation with said terminalblock, said plug housing being received within said receptacle housingand closely surrounding said terminal block when the receptacleterminals are engaged with the plug terminals, a slide member mounted onsaid receptacle housing for transverse sliding movement with respectthereto between opposite extreme positions, said slide member havingmeans defining a first outer relieved area for receiving the plugshoulder when the slide is in one extreme position and having meansdefining a second relieved area parallel to and spaced from the firstarea for successively receiving the plug shoulder when the slide is inits other extreme position, said slide further having means defining achannel connecting the two relieved areas for receiving the plugshoulder as the slide is moved between its extreme opposite positions,said channel and relieved area defining means forming opposed stopshoulders for engaging the plug shoulder to afford a two step delayedwithdrawal and insertion of the plug respectively from and into thereceptacle, a cover hingedly mounted on said slide and biased forclosing the receptacle when the plug is removed therefrom and the slideis in said one extreme position, and means on said receptacle housingengageable with said cover for holding the same open when the slide isin the other extreme position wherein the plug is inserted in placewithin the receptacle.

4. A retardation means for use with explosion proof electricalconnectors including a separable plug having a radial shoulder thereonand a receptacle telescopically receiving the plug, said meanscomprising a slide mounted on said receptacle for movement transverse tothe telescoping axis thereof between opposite positions, said slidehaving relieved areas thereon defining opposed transversely spaced stopshoulders for stepwise engagement with the plug shoulder upon transversemovement of said slide member from one to the other of said oppositepositions so as to atford stepwise delayed insertion and withdrawal ofthe plug respectively into and from the receptacle, a cover hingedlymounted on said slide for closing said receptacle when the plug iswithdrawn therefrom, and means on said receptacle engaging said cover tohold the same open when the slide is in position with the plugcompletely received within the receptacle.

5. An explosion proof receptacle for use with a plug having terminalstherein and a radially extending arcuate shoulder thereon, saidreceptacle comprising a housing having terminals for cooperativelyreceiving the plug terminals, a slide member mounted on said receptaclefor sliding movement transverse to the longitudinal axis thereof andhaving means defining a first outer relieved area for receiving the plugshoulder when the slide is in one extreme position, means defining asecond relieved area parallel to and spaced from the first area forsuccessively receiving the plug shoulder when the slide is in its otherextreme position, and means defining a channel connecting the tworelieved areas for receiving the plug shoulder as the slide is movedbetween its extreme positions, said channel and relieved area definingmeans forming spaced opposed shoulders which serve as stops againstwhich the plug shoulder abuts when the plug is being inserted into andremoved from the receptacle.

6. An explosion proof receptacle for use with a plug having terminalstherein and a radially extending arcuate shoulder thereon, saidreceptacle comprising a housing having terminals for cooperativelyreceiving the plug terminals, a slide member mounted on said receptaclefor sliding movement transverse to the longitudinal axis thereof, saidslide having means defining a first outer relieved area for receivingthe plug shoulder when the slide is in one extreme position, said slidehaving means defining a second relieved area parallel to and spaced fromthe first area for successively receiving the plug shoulder when theslide is in its other extreme position, said slide having means defininga channel connecting the two relieved areas for receiving the plugshoulder as the slide is moved between its extreme positions, saidchannel and relieved area defining means forming spaced opposedshoulders which serve as stops against which the plug shoulder abutswhen the plug is being inserted into and removed from the receptacle, acover hingedly mounted on said slide, and means biasing said cover toclose the receptacle when the plug is removed therefrom.

7. An explosion proof receptacle for use with a plug having a plug bodycarrying a plurality of plug terminals extending therefrom, an annularlyextending plug housing surrounding said plug terminals, and a radiallyextending arcuate shoulder on the outer surface of the plug housing,said receptacle comprising a receptacle body mounting a terminal blockhaving a plurality of receptacle terminals telescopically engageablewith the plug terminals, an annular receptacle housing extending fromsaid receptacle body in spaced surrounding relation with said terminalblock, said plug housing being received within said receptacle housingand closely surrounding s id terminal block when the receptacleterminals are engaged with the plug terminals, a slide member mounted onsaid receptacle housing for transverse sliding movement with respectthereto between opposite positions, said slide member having meansthereon defining transversely spaced stop shoulders for successivelyengaging the plug shoulder upon transverse movement of said slide memberfrom one to the other of said opposite positions so as to afford a twostep delayed withdrawal and insertion of the plug respectively from andinto the receptacle, a cover hingedly mounted on said receptacle housingand biased for closing the receptacle when the plug is removed therefromand the slide is in one of said opposite positions, and means on saidslide engageable with said cover for holding the same open when theslide is in the other of said opposite positions wherein the plug isinserted in place Within the receptacle.

8. An explosion proof receptacle for use with a plug having a plug bodycarrying a plurality of plug terminals extending therefrom, an annularlyextending plug housing surrounding said plug terminals, and a radiallyextending arcuate shoulder on the outer surface of the plug housing,said receptacle comprising a receptacle body mounting a terminal blockhaving a plurality of receptacle terminals telescopically engageablewith the plug terminals, an annular receptacle housing extending fromsaid receptacle body in spaced surrounding relation with said terminalblock, said plug housing being received within said receptacle housingand closely surrounding said terminal block when the receptacleterminals are engaged with the plug terminals, a slide member mounted onsaid receptacle housing for transverse sliding movement with respectthereto between opposite positions, said slide member having meansthereon defining transversely spaced stop shoulders for successivelyengaging the plug shoulder upon transverse movement of said slide memberfrom one to the other of said opposite positions so as to afford a twostep delayed Withdrawal and insertion of the plug respectively from andinto the receptacle, a cover having an arm fixed thereto hingedlymounted on said receptacle housing, means engaged between said arm andsaid receptacle housing for biasing said cover to close the receptaclewhen the plug is removed therefrom and the slide is in one of saidextreme positions, a key member on said slide, and means defining a sloton said cover arm engageable with said key for holding the cover openwhen the slide is in the other extreme position wherein the plug isinserted in place within the receptacle.

9. A retardation means for use with explosion proof electricalconnectors including a separable plug having a radial shoulder thereonand a receptacle telescopically receiving the plug, said meanscomprising a slide mounted on said receptacle for movement transverse tothe telescoping axis thereof between opposite positions, said slidehaving relieved areas thereon defining transversely spaced stopshoulders for stepwise engagement with the plug shoulder upon transversemovement of said slide member from one to the other of said oppositepositions so as to afford stepwise delayed insertion and withdrawal ofthe plug respectively into and from the receptacle, a cover hingedlymounted on said receptacle for closing said receptacle when the plug iswithdrawn therefrom, and means on said slide engaging said cover to holdthe same open when the slide is in position with the plug completelyengaged within the receptacle.

10. An explosion proof receptacle for use with a plug having terminalstherein and a radially extending arcuate shoulder thereon, saidreceptacle comprising a housing having terminals for cooperativelyreceiving the plug terminals, a slide member mounted on said receptaclefor sliding movement transverse to the longitudinal axis thereof andhaving means defining a first outer relieved area for receiving the plugshoulder when the slide is in one extreme position, means defining asecond relieved area parallel to and spaced from the first area forsuccessively receiving the plug shoulder when the slide is in its otherextreme position, means defining a channel connecting the two relievedareas for receiving the plug shoulder as the slide is moved between itsextreme positions, said channel and said first and second relieved areadefining means forming spaced opposed shoulders which serve as stopsagainst which the plug shoulder abuts when the plug is being insertedinto and removed from the receptacle, and said slide having meansdefining a third relieved area parallel to and spaced from said firstand second areas and opening directly into said second area forreceiving the plug shoulder when the plug is completely inserted in thereceptacle and the slide is in an intermediate position thereby lockingthe plug in the receptacle.

11. An explosion proof receptacle for use with a plug having a pluralityof terminals extending therefrom, said receptacle comprising asleeve-like body having an internally threaded bore in one end, aterminal block having at one end a plurality of receptacle terminalstelescopically engageable with the plug terminals, means formed on saidreceptacle for cooperating with the plug so as to orient said receptacleterminals in substantially axial alignment with the plug terminals, theother end of said block having an external threaded portion forthreadably engaging within said threaded body, means defining a shoulderon the threaded end of said block, said block having an enlarged arcuaterelieved portion adjacent said shoulder, and means on said bodyextending into said enlarged arcuate relieved portion and looselyengaging said shoulder, whereby said terminal block is free for limitedrotation with respect to said sleeve-like body so that the receptacleterminals align themselves with the plug terminals when the plug isinserted into the receptacle while maintaining said receptacle explosionproof.

12. An explosion proof receptacle for use with a plug carrying aplurality of plug terminals, said receptacle comprising a body having athreaded bore in one end thereof and an enlarged annular housing portionextending from the other end thereof, a terminal block mounted withinsaid annular housing and having at one end a plurality of receptacleterminals telescopically engageable with the plug terminals, meansformed on said housing for cooperating with the plug so as to orientsaid receptacle terminals in substantially axial alignment with the plugterminals, the other end of said block having a threaded portion forengaging within said threaded body, said threaded portion terminating ina reduced diameter portion defining a radial shoulder, said reduceddiameter portion of said block having an arcuate notch adjacent saidshoulder, and means on said body loosely engaging said shoulder andextending into said arcuate notch for preventing the withdrawal of saidterminal block from said body whereby said block is free for limitedrotation within said body so that said receptacle terminals alignthemselves with the plug terminals when the plug is inserted into thereceptacle while maintaining said receptacle explosion proof.

13. An explosion proof receptacle for use with a plug carrying aplurality of plug terminals, said receptacle comprising a body having athreaded bore in one end thereof and an enlarged annular housing portionextending from the other end thereof, a terminal block mounted withinsaid annular housing and having at one end a plurality of receptacleterminals telescopically engageable with the plug terminals, meansformed on said housing for cooperating with the plug so as to orientsaid receptacle terminals in substantially axial alignment with the plugterminals, the other end of said block having a threaded portion forengaging within said threaded body, said threaded portion terminating ina reduced diameter portion, and means on said body loosely engaging saidblock for preventing the Withdrawal of said terminal block from saidbody while permitting limited relative rotational movement between saidblock and said body, whereby said receptacle terminals align themselveswith the plug terminals when the plug is inserted into the receptacleWhile maintaining said receptacle explosion proof.

Riley Apr. 29, 1924 Cannon Apr. 22, 1930 14 Meuer Oct. 18, 1932To'rnblom Apr. 12, 1938 Wulle et al May 5, 1942 Richardson et al Nov.30, 1948 Quackenbush Apr. 15, 1952 Howard et al Jan. 27, 1953 CastelliDec. 14, 1954 Swanson et al Aug. 9, 1955 Petree Sept. 10, 1957 FOREIGNPATENTS Switzerland June 15, 1959

1. AN EXPLOSION PROOF RECEPTACLE FOR USE WITH A PLUG HAVING A PLUG BODYCARRYING A PLURALITY OF PLUG TERMINALS EXTENDING THEREFROM, AN ANNULARLYEXTENDING PLUG HOUSING SURROUNDING SAID PLUG TERMINALS, AND A RADIALLYEXTENDING ARCUATE SHOULDER ON THE OUTER SURFACE OF THE PLUG HOUSING,SAID RECEPTACLE COMPRISING A RECEPTACLE BODY MOUNTING A TERMINAL BLOCKHAVING A PLURALITY OF RECEPTACLE TERMINALS TELESCOPICALLY ENGAGEABLEWITH THE PLUG TERMINALS, AN ANNULAR RECEPTACLE HOUSING EXTENDING FROMSAID RECEPTACLE BODY IN SPACED SURROUNDING RELATION WITH SAID TERMINALBLOCK, SAID PLUG HOUSING BEING RECEIVED WITHIN SAID RECEPTACLE HOUSINGAND CLOSELY SURROUNDING SAID TERMINAL BLOCK WHEN THE RECEPTACLETERMINALS ARE ENGAGED WITH THE PLUG TERMINALS, A SLIDE MEMBER MOUNTED ONSAID RECEPTACLE HOUSING FOR TRANSVERSE SLIDING MOVEMENT WITH RESPECTTHERETO BETWEEN OPPOSITE POSITIONS, SAID SLIDE MEMBER HAVING MEANSTHEREON DEFINING OPPOSED TRANSVERSELY SPACED STOP SHOULDERS FORSUCCESSIVELY ENGAGING THE PLUG SHOULDER UPON TRANSVERSE MOVEMENT OF SAIDSLIDE MEMBER FROM ONE TO THE OTHER OF SAID OPPOSITE POSITIONS SO AS TOAFFORD A TWO STEP DELAYED WITHDRAWAL AND INSERTION OF THE PLUGRESPECTIVELY FROM AND INTO THE RECEPTACLE, A COVER HINGEDLY MOUNTED ONSAID SLIDE AND BIASED FOR CLOSING THE RECEPTACLE WHEN THE PLUG ISREMOVED THEREFROM AND THE SLIDE IS IN ONE OF SAID OPPOSITE POSITIONS,AND MEANS ON SAID RECEPTACLE HOUSING ENGAGEABLE WITH SAID COVER FORHOLDING THE SAME OPEN WHEN THE SLIDE IS IN THE OTHER OF SAID OPPOSITEPOSITIONS WHEREIN THE PLUG IS INSERTED IN PLACE WITHIN THE RECEPTACLE.